Interest

Money can grow over time.

You can pay extra to borrow money. Or you can get extra when you save. This extra money is called interest.

People used interest a long time ago. In old lands, they used it for grain. They also used it for metal.

Some people thought interest was wrong. They did not want to charge it.

Interest can grow even more. This is called compound interest. It happens when you earn interest on your interest. This makes the money grow fast. It is a way to make money grow.

Interest is extra money paid for using someone else's funds.

If you borrow money, you pay interest to the lender. If you save money, the bank pays interest to you. This extra amount is based on a rate, like a percentage.

People used interest a very long time ago. Old records from Sumeria show people used it for grain and metal.

Some people thought charging interest was wrong. For example, early Christian and Islamic leaders had rules against it. They often called this "usury." They felt it was unfair to make money from money.

There are two main ways to calculate it. Simple interest is only on the first amount you borrow. Compound interest is different. It is interest earned on top of old interest. This makes money grow much faster. A man named Jacob Bernoulli studied this math. His work helped find a special number called "e."

Today, banks use these rules to help people save and grow wealth.

Interest is a way for money to move between people. When someone borrows money, they pay back more than they originally took. This extra amount is called interest. It is paid at a specific rate, often shown as a percentage. For example, a person might pay a bank to borrow money for a house.

On the other hand, a person can earn interest by saving money. In this case, the person is the lender and the bank is the borrower. Interest is different from a fee or a dividend. A dividend is a share of profit paid to owners of a company. Interest is a set amount decided before the money is even moved.

There are two main ways to calculate how interest grows. Simple interest is only calculated on the starting amount, called the principal. If you borrow money with simple interest, the extra cost stays the same each time. Compound interest is more powerful because it includes interest earned on old interest. This means the total amount grows faster and faster over time.

A mathematician named Jacob Bernoulli studied this growth. His work on compounding helped scientists discover a special number called "e." Most banks calculate interest on a daily, monthly, or yearly basis. This rate changes how much a debt or a saving grows.

People have used credit for thousands of years. Records from Sumeria from 3000 BC show people used credit for grain and metals.

Historians think the idea of interest grew from leasing animals or seeds. For example, a borrowed animal could have babies, creating more value. By 2400 BC, there is written evidence of compound interest. At that time, the annual interest rate was about 20 percent. These early systems helped farming and cities grow. However, different cultures had very different rules about whether charging interest was right.

Many religions and leaders had strong views on interest. Early Jewish rules had prohibitions against usury, which is charging interest. In the year 325, the First Council of Nicaea forbade clergy from usury. They defined usury as lending at more than 1 percent per month. Later, the Catholic Church argued that interest was wrong because it was "double charging." They felt it was unfair to charge for both a thing and its use. In Islamic civilization, many scholars agreed that the Qur'an forbids charging interest. This led to the rise of interest-free Islamic banking in the late 20th century.

Today, interest plays a huge role in the world economy. Economists call the interest rate the "price of credit." In a free market, the rate is shaped by supply and demand. If there is not much money to lend, rates might go up. Different thinkers have explained why interest exists over the centuries. The School of Salamanca said interest covers the risk of a lender not being paid back. Another thinker, Martín de Azpilcueta, said interest compensates for the time a lender waits.

These ideas help us understand how money works in our modern lives.

Interest is a fundamental concept in finance and economics. It represents a payment made from a debtor to a lender. This payment is an amount above the principal sum, which is the original amount borrowed or deposited. The payment occurs at a specific rate, often expressed as a percentage. Interest is distinct from a fee, which is a charge paid to a third party or a lender. It is also different from a dividend. A dividend is a share of profit paid to company owners. Unlike interest, a dividend is not decided at a specific rate beforehand. Instead, it is a pro rata share of the rewards gained from business risks.

There are two primary ways to calculate interest: simple and compound. Simple interest is calculated only on the principal amount or the remaining principal. It does not include the effect of previous interest payments. In contrast, compound interest includes interest earned on prior interest that has already accumulated. This means the total amount of debt or savings grows exponentially over time. Because of this compounding effect, the frequency of calculation matters. Interest is often calculated on a daily, monthly, or yearly basis. The mathematical study of this rapid growth led to the discovery of the constant *e*. This constant was identified by the mathematician Jacob Bernoulli while studying compounding.

History shows that credit existed long before the invention of coinage. The earliest records come from Sumerian documents dating to 3000 BC. These documents show a systematic use of credit to loan metals and grain. Historians suggest the concept of interest may have evolved from leasing animals or seeds. For example, a borrowed animal could reproduce, creating more value for the lender. By roughly 2400 BC, there was written evidence of compound interest. At that time, the annual interest rate was approximately 20 percent. These early systems were essential for the development of agriculture and urbanization.

Throughout history, various cultures and religions have had conflicting views on interest. In ancient Jewish traditions, there were prohibitions against usury, which is the charging of interest. In 325 AD, the First Council of Nicaea forbade clergy from engaging in usury. They defined usury as lending at a rate higher than 1 percent per month. This was equivalent to a 12.7 percent annual percentage rate. During the Middle Ages, the Catholic Church's opposition to interest became even stronger. The theologian St. Thomas Aquinas argued that interest was a form of "double charging." He believed it was wrong to charge for both the object and its use.

In Islamic civilization, interest has also been a subject of significant religious debate. Most scholars agree that the Qur'an explicitly forbids charging interest. This led to the development of unique financial instruments to encourage lending while following religious laws. In the latter half of the 20th century, interest-free Islamic banking emerged as a major movement. This system applies Islamic law to the modern economy. Instead of charging interest, lenders act as partners. They share both the risks and the profits of an investment. All transactions in this system must be asset-backed and cannot charge interest or service fees.

In modern economics, the interest rate is viewed as the price of credit. It also functions as the cost of capital. In a free market, interest rates are determined by the law of supply and demand. If loanable funds are scarce, interest rates generally tend to be higher. Many different schools of thought have attempted to explain these fluctuations. The School of Salamanca argued that interest compensates a lender for the risk of default. Another thinker, Martín de Azpilcueta, proposed a "time preference" argument. He suggested that interest is compensation for the time a lender must wait to use their money.

Various economists have refined these theories over the last century. In the late 19th century, Swedish economist Knut Wicksell developed a theory based on the difference between natural and nominal interest rates. His work was later expanded by Bertil Ohlin and Dennis Robertson into the loanable funds theory. Other influential figures include Irving Fisher and John Maynard Keynes. These theories help explain how interest rates influence economic crises and overall stability. Understanding interest is essential for grasping how global financial systems and individual economies function today.